Process for preparing ethyl paranitrophenyl thionophenylphosphonate



Unite Patented Jan. 1,-1963 A. Reactions 1 and 2 may be combined, sequentially,

3,071,608 eliminating the separation of an intermediate. rnog n gsmgpl fi ggg gggg fi giq B. The amount of benzene used is greatly reduced, i.e., Thomas M Beck, Homewood, and George L Klein Park about 0.80 ml. of inert solvent per gram of principal Forest, 111., assignors to Victor Chemical Works, Chi- 5 reactanfs' cage, 11! a corporation of Illinois C. Eifective size or level of the charge, and thus produc- No Drawing. Filed Dec. 11, 1958, Ser. No. 779,555 non, p r charge, greatly mcreased- 3 Claims. (Cl. 260-461) D. Troublesome thickening of the charge is eliminated,

thus improving heat transfer and shortening the reac- This invention relates to an improved method for tion time. making ethyl paranitrophenyl thionophenylphosphonate. More specifically, this invention relates to an improved method for making ethyl paranitrophenyl thionophenyl- The over-all reaction according to our new process proceeds as follows:

phosphonate which provides for a significant increase in 065F501 CQHOH OZNCiHOH zwlHmN production and plant efiiciency, a reduction in solvent losses, and the elimination of processing steps. meltsolvent We have discovered that improved, and certainly un- S expected, results are obtained when ethyl paranitrophenyl thionophenylphosphonate is prepared by reacting phenyl- Carla-0cm phosphonothioic dichloride sequentially with ethanol and 20 CtHtNOfl paranitrophenol in benzene and in the presence of tri- The following examples illustrate the process of this ethylamline. invention. Examples 1, 2 and v3 show the use of triethyl- Ethyl Paranitmphenyl thiOHOPhBIIYIPhOSPhOHaTB, hefeamine, trimethylamine and pyridine, respectively. All of after designated as is a l g z d n ithe reactants used in the examples (i.e., Examples 1-3) cide. It may be manufactured under prior art processes were the ordinary commercial grade of chemicals. The h a thOSe dlSClOSBd 111 Patent In this 2-B alcohol referred to therein is a standard denatured patent, the final product is made by a two-step reaction ethanol containing 0.5 percent benzene process which involves, first, the preparation of ethyl thionophenylphosphonyl chloride and, second, the reac- EXAMPLE 1 tion of this compound with sodium p-nitrophenate to 150 cc. of benzene were placed into a flask equipped form the EPN. These reactions may be illustrated as with thermometer, agitator and condenser, including a follows: calcium chloride tube. This was topped by distilling off (1) The patent further points out that Reaction 1, supra, may cc. The contents were then cooled and 66.3 grams be carried out using ethanol and a hydrogen chloride 45 of C H PSCI were added. The condenser was replaced acceptor such as pyridine, as would be illustrated by the with a dropping funnel and a mixture of 15.3 grams of following equation: 2-B ethanol and 36.5 grams of triethylarnine was then PC12+O2H5OH+C5H5N POCIH+CflH5N'HCl solvent These prior art reactions, as illustrated above, are caradded at a temperature of 354() C. over a period of 27 ried out in the presence of relatively large portions of minutes. The reaction was slightly exothermic and after inert solvent (e.g., benzene). A study of the examples the temperature ceased to rise spontaneously, the slightly reveals that the amount of inert solvent is approximately viscous mixture was stirred for an additional two hours 1.3 ml. per gram of the principal reactants (the term at 3840 C. 43.1 grams of paranitrophenyl were then principal reactants is sometimes herein intended to refer added, slowly at first so as to control temperature rise, to the phosphorus compound, ethanol or its derivatives, thereby eifecting a final temperature of 25 (1.; it disand paranitrophenol or its derivatives) in the reactions solved quickly and completely. 30.2 grams of triethylillustrated by Reactions 1 and 1a, supra. In the reaction amine were then added over a period of 20 minutes, illustrated by Reaction 2, supra, the amount of inert thereby bringing the temperature to 60 C. The mixture solvent is approximately 1.6 ml. per gram of the principal thickened somewhat, .but was stirred for an additional 45 reactants. This gives an over-all usage of approximately minutes at 55-60 C. It was then cooled, 250 cc. of 1.5 ml. of inert solvent per gram of principal reactants. water were added plus an additional 200 cc. of benzene.

We have now found that by the use of triethylamine as It was then shaken, separated and washed twice again the hydrogen chloride acceptor in combination with the with 250 cc. portions of water. The benzene was rebenzene solvent, the following advantages result: moved from the product layer by distillation to give 91.3

3 grams of ethyl paranitrophenyl thionophenylphosphonate, which represents a 90% yield. It should be noted that the final 200 cc. of benzene and the water washes were merely used in removing and separating the product and were not necessary to the actual reaction. In the actual reaction, only 0.82 ml. of benzene per gram of principal reactants was used. I

EXAMPLE 2 375 cc. of benzene were added in a one liter flask, equipped witha thermometer, stirrer, condenser and soda lime tube. This was topped by distilling off 50 cc. Then, 105.5 grams of C H PSCl were added. The condenser was then replaced with a dropping funnel containing a previously prepared solution of 33.5 grams of trimethylamine in 24 grams of 2-B ethanol. This mixture was added dropwise over a period of 15 minutes at a temperature of 35-40 C., using ice-water cooling. The mixture was then stirred at this temperature for an additional thirty minutes. 69.5 grams of paranitrophenol where then added, slowly at first to prevent temperature rise. A heavy precipitate formed which prevented complete stirring and necessitated the addition of 50 cc. of benzene. This addition effected satisfactory stirring and the temperature was then raised to 60 C. 30.0 grams of trimethylamine were then added by distilling into the reaction fiask through a tube extending below the surface of the reaction mixture. The temperature was held at 60 C. during the addition. The mixture again became too thick to stir, therefore, another 50 cc. of benzene were added. This was not sufficient for good stirring so the agitator speed was doubled from 300 rpm. to 600 r.p.m. The total addition time was 50 minutes, after which it was held an additional 15 minutes at 60 C. The product was then washed, stirred and separated three times with 375 cc. portions of Water. The first Wash water was further extracted with an additional 160 cc. of benzene. The benzene was removed by distillation to give 145.5 grams (90%) of EPN. This reaction required 1.42 ml. of benzene per gram of principal reactants.

EXAMPLE 3 300 ml. of benzene were placed in a 500 ml. flask, equipped with thermometer, stirring rod and condenser. This was topped by distilling off 100 ml. The remainder was cooled and 66.3 grams of C H PSCI were added. The condenser was then replaced with a dropping funnel and a mixture of 15.3 grams of anhydrous 2-B ethanol and 28.5 grams of pyridine were added at 35-40 C. over a 20 minute period. The mixture was then stirred for an additional 2 /2 hours at 40 C. This resulted in the formation of a heavy sludge of pyridine hydrochloride. The addition of 42.0 grams of paranitrophenol formed a still heavier, almost unstirrable sludge. 23.6 grams of pyridine were then added over a 15 minute period with no observable heat of reaction. The temperature was raised to 50 C. during the latter part of the addition and was then held at 60 C. for one hour. There was no apparent change in the amount of solid pyridine hydrochlonide. The mixture was then cooled, mixed with 100 ml. of benzene and sufficient water to dissolve the amine salt, and transferred to a separatory funnel where it was washed three times with 250 m1. portions of water. The benzene was thenremoved from the product layer by distilling to a final temperature of 70 C. at 5 mm. of mercury pressure. 89 grams of product was produced, which had a melting point of 40 65" C. This was low purity material in view of the :37 C. melting point of the 'pure' product. This reaction required 1.66 ml. of benzene per gram of principal reactants.

The results of the preceding experiments (i.e., Examples-1 3, supra) are summarized in Table I, infra.

1 Paranitrophenol.

The data that are set forth in Table I, supra, clearly indicate that llIl spite of the reduced amount of benzene which is used with the triethylamine, the reaction proceeds smoothly in all respects and produces a good product with minimum difficulties.

The temperatures and general reaction conditions for carrying out this invention are not of a critical nature. The addition of the ethanol-triethylamine mixture is preferably carried out at 35-40 C. but temperatures up to the boiling point of the mixture may be used. The final addition of triethylamine following the paranitrophenol addition is preferably carried out at temperatures below 60 C.; however, higher temperatures, up to the boiling point of the reactants, may be used. In each case the temperature range is more nearly controlled by the equipment limitations rather than the critical nature of the reaction itself.

The proportions of all reactants used in our reaction are approximately stoichiometric based upon the amount of phenylphosphonothioic dichloride which is used. It

adensity of only 0.879 gm./m1., a prior art ratio of 1.42

ml./gm. is equal to a ratio of 1.1 gm. of benzene per gram of reactants. On the other hand, the present invention, which results in a ratio of 0:82 ml./gm., is equal to a ratio of 0.722 gm. of benzene per gram of reactants.

' Thus, whereas the prior art method used a weight of benzene in excess of the weight of the reactants, in the present invention the amount of benzene that is used may be as low as 0.70 that of the weight of the reactants.

The terms ethanol and paranitrophenol are hereinafter intended to include suitable salts such as sodium ethylate and sodium paranitrophenolate.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.

We claim:

1. The method of producing ethyl paranitrophenyl thionophenylphosphonate comprising: reacting phenyl-' phosphonothioic dichloride sequentially with ethanol and paranitrophenol till the presence of benzene and triethylamine, the weight of the benzene used not exceeding the combined weight of phenylphosphonothioic dichloride, ethanol and paranitrophenol; and recovering ethyl paranitrophenyl thionophenylphosphonate.

2. The method of producing ethyl paranitrophenyl thionophenylphosphonate comprising: reacting phenylphosphonothioic dichloride sequentially with substantially stoichiometric proportions of ethanol and paranitrophenol in the presence of benzene and a substantially stoichiometnic amount of triethylamine, the :weight of the benzene used not exceeding the combined weight of phenylphosphonothioic dichloride, ethanol and paranitrophenol; and

recovering ethyl paranitrophenyl thionophenylphosphonate.

3. The method of producing ethyl paranitrophenyl thionophenylphosphonate comprising: combining substantially stoichiometric amounts of ethanol and triethylamine With the combination of phenylphosphonothioic dichloride and benzene; sequentially incorporating a substantially stoichiometric amount of paranitrophenol and a second substantially stoichiometric amount of triethylamine into the reaction mixture, the Weight of the benzene used not exceeding the combined Weight of phenylphosphonothioic dichloride, ethanol and paranitiophenol; and trecover-ing ethyl paranitrophenyl thionophenylphosphonate.

References Cited in the file of this patent UNITED STATES PATENTS 

1. THE METHOD OF PRODUCING ETHYL PARAMITROPHENYL THIONOPHENYLPHOSPHONATE COMPRISING: REACTING PHENYLPHOSPHONOTHIOIC DICHLORIDE SEQUENTIALLY WITH ETHANOL AND PARANITROPHENOL IN THE PRESENCE OF BENZENE AND TRIETHYLAMINE, THE WEIGHT OF THE BENZENE USED NOT EXCEEDING THE COMBINED WEIGHT OF PHENYLPHOSPHONOTHIOIC DICHLORIDE, ETHANOL AND PARANITROPHENOL; AND RECOVERING ETHYL PARANITROPHENYL THIONOPHENYLPHOSPHONATE. 